Choosing input channel with V4L2 API

Question

I want to choose the input channel of my VideoCamera device. I can select it in VLC over the "Settings-Dialog". In Advanced Settings I can switch 'input' to 3 and my camera works. Now I want to do this in my C++ Application. I cannot find the write method to do this. At the moment my pictures are just black. I need to choose the S-Video Channel of my device.

Answer 1

You should have a look at the source code of v4l2-ctl which is part of v4l-utils. This tool is written in C++/Qt and should provide you with all information you need to do it yourself. Changing the input for a device is handled in v4l2-ctl-io.cpp

void io_set(int fd)
{
    if (options[OptSetInput]) {
        if (doioctl(fd, VIDIOC_S_INPUT, &input) == 0) {
            struct v4l2_input vin;

            printf("Video input set to %d", input);
            vin.index = input;
            if (test_ioctl(fd, VIDIOC_ENUMINPUT, &vin) >= 0)
                printf(" (%s: %s)", vin.name, status2s(vin.status).c_str());
            printf("\n");
        }
    }
    // snip...
}

Hope this helps.

Edit: Just found the relevant part in the official API documentation here. They have some examples on that page how to change the video input.